Seeking integrated network management nirvana

Ethernet and WLANs: Different networks, different services?

Industry analysis by expert Joanie Wexler, plus links to the day's wireless news headlines

The ability to provision, manage and secure wired and wireless LANs as a single entity is a level of network nirvana sought by a number of LAN administrators. Note, however, that not all services work the same way on the wired and wireless sides of the Ethernet switch, given that LAN and WLAN protocols are different.

Evolution of Ethernet

Configuring such services, then, requires some different configuration steps that apply specifically to each network. Among the disparate wired and wireless services:

To continue reading, register here and become an Insider. You'll get free access to premium content from CIO, Computerworld, CSO, InfoWorld, and Network World. See more Insider content or sign in.

The ability to provision, manage and secure wired and wireless LANs as a single entity is a level of network nirvana sought by a number of LAN administrators. Note, however, that not all services work the same way on the wired and wireless sides of the Ethernet switch, given that LAN and WLAN protocols are different.

Evolution of Ethernet

Configuring such services, then, requires some different configuration steps that apply specifically to each network. Among the disparate wired and wireless services:

* Multicast

* Quality of service (QoS)

* Intrusion detection and prevention functions and capabilities

Why are they different? Let's start with multicast.

We all became familiar with multicast when video over the Internet and corporate IP networks emerged. IP Multicast, of course, is a standard way of forwarding bandwidth-intensive content in a network-efficient way, such that a single stream is sent only once and delivered only to the clients interested in receiving it.

This differs from broadcast, which blasts out a transmission to all clients, wasting bandwidth on transmissions to disinterested clients. And it differs from traditional unicast traffic, which does go only to clients that want it. But the stream is sent over and over again, which is less bandwidth-efficient.

So multicast is the "best of both worlds" protocol for content delivery traffic. And this works well on wired IP networks.

What about when that traffic spills over onto the WLAN?

Wi-Fi 802.11 standards dictate how you transport traffic across the shared wireless medium, and multicast isn't specified, explains David Stiff, a senior manager in the wireless networking business unit at Cisco.

Instead, the standard dictates that multicast packets automatically turn into broadcast packets when they hit the Wi-Fi airwaves. This results in a few wireless inefficiencies you might wish to know about:

* Suboptimal reliability, because packet receipt acknowledgements aren't sent with broadcast traffic.

* Automatic, lowest-common-denominator transmit speed to be "fair" to older Wi-Fi protocols still in the network, such as 802.11b and g.

* Unneeded "noise" (interference) in the environment.

Knowing the differences in the services is helpful for setting expectations about how traffic will behave when it moves off one kind of network and onto the other. If you're considering your WLAN a key component of your enterprise content delivery network, ask your vendor if it has any tricks for taming the ill effects of unneeded broadcast packets on the WLAN.

For its part, Cisco has a capability called VideoStream, announced early this year, that acts as a "floodgate" and turns a multicast packet into a unicast packet instead of a broadcast packet, and sends it only to laptops that are listening for it, notes Stiff.

Other vendors might have other solutions, too -- an example of the layer of valuable services that are emerging as most of the Wi-Fi vendors catch up to one another at the “plumbing” level.

Joanie Wexler is an independent networking technology writer/editor in Silicon Valley.